This invention relates to hot mix asphalt (HMA) paving. More specifically, this invention relates to methods and systems for applying a trackless pre-coat of tack or emulsion as part of HMA paving. Note, the present system and method could also be used for warm mix asphalt paving or seal coating or similar applications.
Several techniques and numerous equipment arrangements for the pre-coating tack or emulsion in “hot mix” or “HMA” paving are known from the prior art. For example, a pre-coat of tack has been applied in the past as follows: a tanker truck with tack emulsion therein and a spray bar thereon sprays the road surface with tack. The paver then applies a new layer of HMA over the tack and the old HMA layer; however, the paver leaves tracks in the tack, so that the new layer of HMA does not have uniform bonding to the lower older layer of HMA because of the tracks in the tack coat. Non-uniform bonding of the new HMA layer can result in premature deterioration of the road surface.
At least one road building equipment manufacturer has developed a specially designed spray paver. It utilizes a gravity fed hopper of HMA to a screed and a full paver width tack or emulsion spray bar behind the rear wheels and ahead of the screed.
While these methods are well known in the art, they have the following drawbacks. The gravity fed paver has inherent problems, such as difficulty in loading HMA directly from trucks and a limited HMA load capacity. Also, the specially designed limited (not general purpose) paver is much more expensive than a much more versatile general purpose paver which can be used with or without a detachable asphalt/emulsion pre-coat cart of the present invention.
Consequently, there exists a need for an efficient system and method for applying a tack pre-coat during HMA asphalt paving.